Due to various advantages such as small size, high brightness at low power consumption, long lifespan, and low manufacturing costs, light emitting diodes (LEDs) are used in a display unit or a lighting apparatus which replaces a typical light bulb.
Depending upon luminous characteristics, light emitting diodes can be classified into IR light emitting diodes configured to emit IR light, visible light emitting diodes configured to emit visible light, UV LED (light emitting diode)s configured to emit UV light, and the like.
Among such light emitting diodes, UV LEDs have been applied to a sterilization apparatus with various advantages, such as inexpensiveness, user convenience and high efficiency, in various fields, since effects of UV light in removal of DNA or RNA bacteria were ascertained.
For example, the UV LED is used in a sterilization apparatus provided to various products, such as household refrigerators, warehouse refrigerators, vehicle-mounted refrigerators, kimchi refrigerators, cup sterilizers, shoes deodorizers, and the like, to remove bacteria and odors.
Typically, a lighting apparatus using a light emitting diode is provided in a structure wherein a printed circuit board having a light emitting diode mounted thereon is provided to a socket and a cover formed of a transparent or translucent acryl or glass material surrounds the light emitting diode.
A lighting apparatus using a UV LED requires a cover formed of a material exhibiting high UV light transmittance due to wavelength characteristics of UV light emitted from the UV LED.
Examples of materials for the cover suitable for such a UV LED lighting apparatus include quartz, a poly(methyl methacrylate) (PMMA) resin, and the like, which exhibit high UV light transmittance.
However, despite high UV light transmittance, such materials are not suitable for the UV LED lighting apparatus due to difficulty in machining such as bending and punching, and low machinability.